empty; hollow; insubstantial; fruitless
Describes arguments, discussions, theories, or plans that lack real content, substance, or practical results. Often used in critical or analytical contexts.
His proposal was hollow and lacked concrete details.
Continuing fruitless discussions won't produce anything.
The policy debate ended up being an empty argument.
His speech sounded hollow.
The theory somehow felt hollow.
無意味 means broadly 'meaningless', whereas 空疎 more narrowly implies that something has form or words but no real content.
虚しい is an i-adjective expressing a feeling of futility or emptiness, while 空疎 is a na-adjective specifically criticizing arguments or plans for lacking substance.
充実 describes something full and substantial, the direct opposite of 空疎, which describes something hollow and lacking content.
空想 (くうそう, 'fantasy/daydream') sounds very similar to 空疎 (くうそ) but describes imaginative thought, not the criticism of an argument as hollow.
Compound of 空 (empty) and 疎 (sparse, neglect). The combination emphasizes a lack of dense or substantial content, used figuratively for ideas and arguments.